1. Field of the Invention
This invention relates generally to fluid exchange systems and in particular to those useful in the exchanging of fluids of the types found in motor vehicles and pressurized hydraulic systems. Disclosed herein is a fluid exchange apparatus wherein used hydraulic fluid is exchanged for fresh fluid by interposing the invention in-line with a hydraulic fluid circulation circuit. The exchange apparatus may utilize pressurized spent fluid flow as a fluid power medium to activate the auto-replenishing fluid exchanger system to replace the spent fluid with fresh fluid at equalized flow rates. Alternatively, the exchange apparatus may be externally powered to replace the spent fluid with fresh fluid at equalized flow rates.
2. Related Background Art
A variety of hydraulic fluid exchange systems are known to those skilled in the art. One early example is the applicant""s U.S. Pat. No. 5,318,080, which featured a pressure vessel divided into two chambers by a flexible diaphragm (See, FIG. 3). To refill this exchange system with fresh fluid in preparation for the exchange operation, fresh fluid was introduced into one chamber causing the diaphragm to distend and simultaneously force the spent fluid out of the second chamber. A particular characteristic of this device was the limited volumetric capacity of the pressure vessel, as the capacity of fluid exchange was substantially equal to the volume of the contained fresh fluid prior to the exchange process. If the volume of fresh fluid contained in fresh-fluid charged receiver was less than the desired exchange capacity, one would have to interrupt the exchange process upon discharge of the fresh fluid load, recharge the receiver with fresh fluid, and then reinstate the exchange process until the desired fluid capacity was exchanged. Merely increasing the volumetric capacity of the fluid receiver would concomitantly increase manufacturing costs, fluid friction losses, and the overall size of the exchange apparatus. As a result, the efficiency of such a device was limited by the volume of fresh fluid the device was able to contain.
An additional limitation of prior art exchange systems has been the requirement of on-board fluid tanks for holding fresh fluid and used fluid requirements. These tanks increase the overall size and weight of an exchange apparatus, making movement and storage of the fluid exchange apparatus burdensome.
The present invention solves many of the problems existent in prior hydraulic fluid exchange systems. The present invention provides a compact fluid exchange system having a fluid receiver which is substantially smaller than the amount of fluid exchanged during the exchange process. As the size of the fluid receiver in the present invention is not related to the volume of ultimately fluid exchanged, the apparatus can be used to service hydraulic fluid systems having a variety of circuit sizes, configurations, etc.
Briefly, the invention includes a reciprocating pump assembly having a pair of pumping chambers and a pair of working chambers. The pump assembly operates to receive used fluid from an accessed hydraulic fluid circuit into one of the working chambers, introduce fresh fluid from a pumping chamber into the hydraulic fluid circuit, simultaneously refill the other pumping chamber with fresh fluid, and simultaneously discharge spent fluid from the other working chamber into a spent fluid receptacle. Fluid flow relative to the pump assembly is directed by a control structure. This reciprocating pump assembly cycles until the predetermined exchange volume is satisfied (determined by such means as visual or optical comparison of fluid input and output, sensor devices, etc.). The invention permits connection to both a bulk fresh fluid supply and a floor drain, such as those typically found in vehicle repair facilities.
One object of the invention includes a reciprocating pump assembly having a power medium of a pressurized hydraulic fluid, such as used transmission fluid of an operating motor vehicle during a maintenance procedure, or pressurized fresh fluid from an external source.
One object of the invention provides a fluid exchange apparatus released from the requirement of having dedicated on-board fluid reservoirs. A remote bulk fresh fluid supply and remote waste fluid receptacle, such as those found in vehicle repair facilities, may be utilized to practice the present invention. In this manner, a smaller, more compact fluid exchange apparatus is provided.
One object of the present invention permits an efficient change between different fresh fluids (grades, additive packages, etc.) between or during exchange procedures. The limited volumetric capacity of the pump assembly and associated conduit results in a limited amount of the previous different fresh fluid charge held within the exchange apparatus.
Another object of the invention includes a reciprocating pump assembly having an external power source, such as an electric motor, for powering or assisting in the powering of the pump assembly. Additionally, a booster pump assembly may be provided to assist in the exchange procedure for certain hydraulic environments, such as low flow or pressure systems.
Yet another object of the invention provides a boost pump which can be controlled to provide variable levels of fluid pressurization.
Yet another object of the invention provides a boost pump which is fluidly coupled to a used fluid conduit, receiving used fluid from an accessed hydraulic circuit.
Yet another object of the invention provides a boost pump which is fluidly coupled to a fresh fluid conduit, receiving fresh fluid from a fresh fluid source.
Yet another object of the invention provides a range of pump assembly structures for practicing the invention. The pump assembly structures may include a linear pump assembly, a displaced piston/crank assembly, and a rotor pump assembly. These and other objects, features and advantages of the present invention will become apparent to one skilled in the art upon analysis of the following detailed description in view of the drawings.